A large number of techniques for processing an exhaust gas generated from internal combustions have been conventionally proposed. In particular, various techniques for processing an exhaust gas from diesel engine have been proposed for the purpose of reduction of discharge of particulate materials (PM) and NOx contained in an exhaust gas. For example, as catalysts for purifying an exhaust gas, oxidization catalysts which oxidize carbon monoxide (hereinafter also referred to as “CO”) and hydrocarbon (hereinafter also referred to as “HC”) into CO2 and H2O, NOx storage catalysts which store nitrogen oxides (hereinafter also referred to as “NOx”), three-way catalysts which simultaneously remove NOx, CO and HC, and the like have been proposed.
An oxidation catalyst for processing an exhaust gas is required to have high thermal durability since it is exposed to an exhaust gas with a high temperature. For example, Patent Literature 1 discloses refractory inorganic oxide powder, which contains platinum and palladium in a mass ratio of 20/1 to 1/1 as an oxidation catalyst improved in heat resistance.